Model 6514 Quick Results Guide 5
Guarded connections
The basic guarded connections for volts and ohms are shown in Figure 5. With guard
(GRD) on, the driven guard is available at the inner shell of the triax connector which is
connected to the metal guard plate. The driven guard is used to eliminate leakage current
and capacitance in high impedance circuits that could corrupt the volts or ohms
measurement.
WARNING
The guard voltage is at the same potential as the input. Therefore, haz-
ardous voltage on the input will also be present on the guard plate. To
prevent electric shock, always use a metal safety shield (as shown in
Figure 5) for guarded voltage measurements above 30Vrms (42V
peak). The metal safety shield must be connected to safety earth
ground using #18 AWG or larger wire.
WARNING
With an open input, up to 250V peak may be present on the guard ter-
minals while in Volts or Ohms. To prevent a safety hazard, enable zero
check whenever the input is open.
HI
HI
LO
LO
INPUT
250V PK
INPUT
250V PK
COMMON
COMMON
V
Metal Guard Plate
Metal Guard Plate
Metal Safety Shield
Safety
Earth
Ground
Measure Volts
Measure Ohms
Chassis
Ground
GRD
GRD
Ω
NOTE: GRD must be on.
Safety
Earth
Ground
Chassis
Ground
Metal Safety Shield
Figure 5
Basic connections for guarded measurements
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